1. Field of the Invention
This invention relates to a portable handy phone system allowing us to utilize both public radio telephone services and private radio telephone services by the same portable handy phone.
2. Prior Art
Conventionally, the public radio telephone services allow their subscribers to use portable handy phones, represented by automotive vehicle telephones and cellular phones, in a wide outdoor service area. Meanwhile, the private radio telephone services allow their subscribers to use portable handy phones in a limited facility as handset units through radio communication with a base station of a private branch exchange.
The public radio telephone services are expected to have a huge communication zone sufficient to allow subscribers moving outdoor to continuously use their handy phones without interruptions of communication. To this end, a public radio base station for the public radio telephone services is required to be a large scale radio connection apparatus.
On the other hand, the private radio telephone services are limited to in-house uses, which require a relatively narrow communication zone. Thus, a private radio base station is normally a small scale equipment installable in a private facility. Thus, function and mechanism of each portable handy phone is differentiated in accordance with the type of radio telephone service to be used. In other words, conventional portable handy phones are dedicated to only one of these two kinds of radio telephone services.
That is, the public radio telephone services and the private radio telephone services have been conventionally considered as being totally different from each other in view of difference of users, scale of facilities, etc.
However, a demand toward outdoor use of handy phones dedicated to the private radio telephone services is gradually increasing. Meanwhile, if a reduction of communication zone is permitted to a certain degree, it will be feasible to downsize each public radio base station so that the scale of each public radio base station becomes comparable to the facility of the private radio base station.